In a process of fabricating a transistor, a silicon substrate is cleaned with a dilute hydrofluoric acid, a silicon oxide film serving as a gate insulating film is formed, and a polysilicon electrode is formed thereon, and then a source/drain electrode is formed by means of patterning, etching, ion implanting, sidewall forming, and ion implanting. In order to guarantee high performance of the transistor according to miniaturization of the semiconductor device, it is inevitable that technologies relating to a structure of a transistor, formation of a gate insulating film, selection of a material of the insulating film, and a metal gate should be developed.
Recently, SiON and hafnium (Hf)-based HfSiON have been influential as a material of the gate insulating film (see, for example, Patent Documents 1 and 2).
Patent Document 1: Japanese Patent Laid-open Publication No. 2002-170825
Patent Document 2: Japanese Patent Laid-open Publication No. 2005-79223